Evaporation abrupt changes in the Qinghai-Tibet Plateau during the last half-century

Pan evaporation (E_pan) was regarded as a critical indicator of climate change, especially in the Qinghai-Tibet Plateau (QTP). By using the measured daily E_pan data of 274 stations in the QTP from 1970 to 2017, the study detected abrupt changes in annual E_pan series in different spatial scales, through integrating the Mann-Kendall abrupt change test, moving t-test and piecewise linear fitting model. Results showed that abrupt changes existed generally in the QTP where mean and trend abrupt changes were detected in 76.6% and 97.8% of 274 stations during the last half-century. Major abrupt change time of mean values and trends was respectively in around 1996, 1989 and 2007. In comparison, early abrupt changes were observed in the south (south of 30°N) and north (north of 35°N) but late ones in the midland (30-35°N). Corresponding to the low frequent behaviors, pan evaporation paradox only existed in the QTP as a whole in 1970-1990 and was not apparent at site scale, with less than 9.5% of 274 stations detected in different periods. The results confirmed prevailing abrupt change of pan evaporation and its distinct spatial pattern in the QTP.